Evolution and Thermodynamics

A note on "The Evolution of biological complexity"

Adami et al

In The Evolution of biological complexity, Christoph Adami, Charles Ofria and Travis C. Collier analysed the relationship between evolution by natural selection and the entropy of the genome. There are some similarities between their paper and my own analysis of Evolution and the Second Law of Thermodynamics. (Note on dates: The published paper states that PNAS received Adami et al's paper on December 22, 1999. Archives of some of my earlier versions of my analysis can be found on Wayback here and here. This Usenet message suggests that I originally posted the page in 1995 – apparently Wayback doesn't go way back to 1995, at least not for my web pages.)

Although both Adami et al and myself consider the statistical entropy of the genome, and analyse the relationship between entropy and evolution, there are some differences in intent:

Another difference is that Adami et al declare the genomes to be Maxwell's demon. My own understanding is that Maxwell's demon is the little guy opening and shutting the door to let the right molecules through and not let the wrong molecules through. Extending this analogy to evolution, the "right" and "wrong" items are the "good" and "bad" mutations, and the "door" that lets only the good ones in is natural selection, as embodied in the processes of birth, growth, reproduction and death. The reason that Maxwell's demon cannot break the Second law is that the door has to stay open when opened and stay shut when shut, which requires the energy involved in opening and shutting it to be dissipated in each case. The equivalent problem with evolution is that the processes of life, growth, reproduction and death have to dissipate energy, if natural selection is to proceed in a forward direction and not reverse itself. This equivalence leads naturally to the identification of natural selection with Maxwell's demon.

Other Papers

Self-reproducing system can behave as Maxwell's demon: theoretical illustration under prebiotic conditions by J Otsuka and Y Nozawa. Unfortunately not available online unless you pay US$30. It's not too clear from the abstract whether their reference to Maxwell's demon relates specifically to evolution by natural selection.